The weirdest DNS problem I have come upon

I have set up a Linux (Mandriva 2006) server on my home ADSL line and everything works just splendid.

Well, everything except for a tiny little problem. Bind sometimes has a problem with resolving A records, always for the same domains and hosts. But what I don't understand is that when I turn on more debugging in "dig" it shows me that it received the information, but a error claims it didn't

break.com. 172800 IN NS ns1.theplanet.com.
break.com. 172800 IN NS ns2.theplanet.com.ns1.theplanet.com. 172800 IN A 70.86.61.133
ns1.theplanet.com. 172800 IN A 70.86.61.134
ns1.theplanet.com. 172800 IN A 70.87.7.70
ns1.theplanet.com. 172800 IN A 70.87.7.71
ns2.theplanet.com. 172800 IN A 70.86.61.135
ns2.theplanet.com. 172800 IN A 70.86.61.136
ns2.theplanet.com. 172800 IN A 70.87.7.72
ns2.theplanet.com. 172800 IN A 70.87.7.73
;; Received 205 bytes from 192.55.83.30#53(M.GTLD-SERVERS.NET) in 375 ms

dig: couldn't get address for 'ns1.theplanet.com': failure

Click to expand...

As you can see, dig did indeed receive the IP for ns1.theplanet.com, and then claimed it didn't.

The problem doesn't seem to be a network problem, since I can ping the server.